Step drill bits for metal solve a frustrating puzzle: you need several different hole sizes, but you don’t want to swap bits five times per job. A good step bit walks a small pilot hole up to a clean final diameter in one smooth pass, so electricians, plumbers, and serious DIYers can punch through steel, aluminum, or copper without burning through a drawer full of individual twist drills. The catch is that not all step bits behave the same way. Some stumble on hard metal, some wander off center, and some lose their edge after a few holes.
The eight options below span single-bit workhorses, complete sets, and cobalt units built for tougher alloys. Each one is judged on its geometry, material, range, and how it behaves in real workshop scenarios.
Your Options, Compared
Greenlee GSB12 1-3/8″ Step Bit (#12) Metal Cutter
toolant M35 Cobalt Step Drill Bit, TiAlN, 3/8″ Hex Shank
Greenlee GSBSET3 Step Bit Set (#1, #4, #9)
Unibit M35 Cobalt Step Bit, 7/8″-1-3/8″, 19 Step
Greenlee 34403 Multi-Hole Step Bit, 7/8″
5-Piece Unibit HSS Step Bit Set, 1/8″-1-3/8″
3-Piece Unibit HSS Step Bit Set, 1/8″-7/8″
Unibit HSS Step Bit Set, 1/8″-1-3/8″ (5-Piece)
A Deeper Look At The Lineup
The Greenlee GSB12 1-3/8″ Step Bit (#12) is built for the upper end of the step bit range, where most general-purpose bits run out of diameter. It targets trade work where you need to step up to a 1-3/8″ hole without swapping tools, and the split-point tip is shaped to start biting the moment it touches the workpiece.
Greenlee’s patented split-step design helps the bit walk up through material in measured jumps rather than grabbing, so torque stays manageable on a 1/2″ chuck drill. It cuts mild steel, aluminum, brass, copper, and softer non-metallics like plastic, fiberglass, and laminates, which is the exact range a plumber or electrician reaches for daily.
Strengths Worth Knowing
- Reaches the 1-3/8″ diameter range most step bits can’t cover in a single tool.
- Patented split-step geometry promotes faster hole-to-hole work and smoother chip ejection.
- Durable split-point tip starts on contact, reducing the need for a center punch on every hole.
- Compatible with standard 1/2″ chuck drills, the format most corded and high-torque cordless tools use.
Worth Noting
- Single-bit design means you still need smaller step bits for sub-1/4″ pilot work.
- Larger diameters demand steady feed pressure, and rushing tends to shorten bit life faster.
Who It Suits Best
Plumbing and electrical pros punching large holes in steel enclosures, conduit bodies, and junction boxes on a regular basis.
Consider Something Else When
Pick the Greenlee GSBSET3 Step Bit Set (#1, #4, #9) instead, since you want one package covering smaller trade-common diameters.
Where the Greenlee GSB12 1-3/8″ Step Bit (#12) leans on size, the toolant M35 Cobalt Step Drill Bit leans on metallurgy. The M35 cobalt steel base (a high-speed steel alloyed with roughly 5% cobalt) holds hardness at elevated temperatures, which matters when you’re feeding into stainless steel or thick aluminum where friction builds fast.
TiAlN coating (titanium aluminum nitride, a hard ceramic layer that reduces heat transfer) gives the cutting edges a tougher skin, and the four-spiral flute keeps chips moving off the flutes instead of packing in. The 3/8″ hex shank locks into standard chucks and impact drivers, so the bit can ride in whatever drill you already own.
Everyday Wins
- Cobalt M35 body resists softening when temperatures climb during long cuts in hard alloys.
- TiAlN coating reduces wear on the cutting edges over repeated production runs.
- Four-flute geometry clears chips efficiently, so the bit doesn’t choke mid-hole.
- Hex shank suits impact drivers, giving you a one-tool setup for common site drilling.
Trade Offs
- Range tops out at 1-1/8″, so larger knockouts still need a separate bit like the Greenlee GSB12.
- Cobalt pricing sits well above standard HSS, which can sting for a hobby budget.
Best Suited To
Tradesmen and fabricators cutting stainless steel, hard aluminum, or thick-gauge sheet metal where heat resistance is non-negotiable.
Look Elsewhere When
Step up to the Unibit M35 Cobalt Step Bit, 7/8″-1-3/8″, 19 Step, since you need more increments in the upper diameter range.
The Greenlee GSBSET3 Step Bit Set (#1, #4, #9) is the trio most electricians and HVAC techs reach for first. Bits #1, #4, and #9 cover the small, medium, and upper-middle diameters that come up daily in panel work, while sharing the same Greenlee split-step design found in the standalone GSB12 above.
Progressive cutting edges balance aggression against torque, so the bit keeps cutting under load instead of stalling your drill mid-hole. The split-step geometry maximizes chip clearance, which in practice means fewer clogged flutes and more consistent hole walls from job to job.
Positive Takeaways
- Three trade-common sizes in one purchase, no guesswork on which diameters to start with.
- Same Greenlee geometry as the GSB12, so feel and chip behavior stay consistent across the set.
- Progressive edge design balances cutting speed and torque efficiency for handheld drills.
- Proudly manufactured in the USA, with build quality aimed at daily professional use.
Honest Caveats
- Set skips the very large diameters, so the Greenlee GSB12 still needs to come along for big knockouts.
- Three-bit count means gaps in coverage for shops needing every half-step in between.
Right Fit For
Tradesmen building out a fresh step bit kit and wanting the three sizes that earn their keep on day one.
Skip It When
Pick the 5-Piece Unibit HSS Step Bit Set, 1/8″-1-3/8″ instead, since you want continuous size coverage rather than three spaced jumps.
Feature Snapshot
The Unibit M35 Cobalt Step Bit, 7/8″-1-3/8″, 19 Step earns its place when you live in the upper diameter range and want fine size resolution. Nineteen incremental steps between 7/8″ and 1-3/8″ lets you match oddball conduit and knockout sizes without falling back on a hole saw.
Same M35 cobalt recipe as the toolant above, paired with TiAlN coating and a four-flute cutting profile. The combination resists heat and keeps swarf moving, which matters most when you’re stepping deep into a thick steel plate or running a long production run.
Notable Upsides
- Nineteen steps let you dial in unusual conduit and panel hole sizes without extra bits.
- Cobalt M35 base and TiAlN coating handle stainless and thick steel with less heat risk.
- Four-flute design clears chips efficiently during longer, deeper cuts.
Points To Keep In Mind
- Range starts at 7/8″, so smaller pilot and mid-size holes still need another bit.
- Cobalt tooling requires slower feed and steady RPM, and aggressive pushing can shorten life.
Who Should Grab It
Electricians, HVAC installers, and metalworkers running a high volume of upper-range hole sizes in hard materials.
Reach For A Different Pick When
Step down to the toolant M35 Cobalt Step Drill Bit, 1/4″-1-1/8″, since you mostly work in the small-to-mid range instead.
The Greenlee 34403 Multi-Hole Step Bit, 7/8″ is the classic one-bit solution that has anchored toolboxes for years. It covers hole sizes from roughly 1/8″ up to 1-3/8″ in a single stepped profile, so you can swap from a pilot hole to a knockout without changing bits.
Its split tip design penetrates steel faster than older single-point designs and resists walking or skidding when the bit first touches the workpiece. The double-fluted body keeps things balanced, so you can apply less pressure and still get a clean hole in mild steel, copper, brass, aluminum, wood, plastic, and laminates up to 3/8″ thick.
The Good Stuff
- One bit covers the full pilot-to-knockout range most trades use in a single workday.
- Split tip starts on contact and resists wandering, helping hole placement accuracy.
- Double-fluted body keeps cuts balanced, so you push less and the drill works less hard.
- Long-running Greenlee design with deep availability of replacement and accessory bits.
Less Ideal Details
- Single-bit design wears out faster than dedicated cobalt bits in hard alloys like stainless.
- Maximum material thickness is 3/8″ mild steel, so thicker plate requires a different approach.
Whose Shelf It Belongs On
Multi-trade technicians and serious DIYers who want a single bit to cover most common diameters across metals and non-metals.
A Better Fit Elsewhere
Pick the Greenlee GSB12 1-3/8″ Step Bit (#12) instead, since your work focuses on the largest end of the range and you want a fresh, dedicated tool for it.
Quick Facts
The 5-Piece Unibit HSS Step Bit Set, 1/8″-1-3/8″ is a budget-friendly way to fill out a shop drawer with the most-used sizes. Five bits step from 1/8″ all the way to 1-3/8″, so you can handle everything from a small pilot to a 1-3/8″ knockout without buying a single high-end unit.
Forged from standard high-speed steel (HSS) with Rockwell 62–65 hardness, the bits resist heat, wear, and thermal fatigue during typical workshop use. The four-flute geometry keeps cuts smooth, so the bit doesn’t grab or chatter when it walks up through steel, aluminum, or copper.
Advantages To Know
- Five bits cover the full 1/8″ to 1-3/8″ range in one set, so you stop juggling loose bits.
- HSS build handles typical mild steel, aluminum, and copper without issue.
- Four-flute cutting edges promote smooth, controlled cuts at lower pressure.
- Lower price than cobalt or premium sets, which helps on a hobby or starter budget.
Practical Considerations
- Standard HSS hardens out faster than cobalt in stainless and high-heat materials.
- Bits may need occasional touch-ups or replacement sooner under heavy daily use.
Perfect Match For
Home workshop owners and DIYers who want one affordable set covering every common diameter in light to medium metalwork.
Another Choice May Suit
Step up to the toolant M35 Cobalt Step Drill Bit, 1/4″-1-1/8″, since you cut stainless or thicker steel and need the heat resistance.
Feature Rundown
The 3-Piece Unibit HSS Step Bit Set, 1/8″-7/8″ is the lighter entry point in the Bestwork lineup. Three bits cover the small-to-mid range that beginners hit first when drilling pilot holes in junction boxes, light-gauge steel, or sheet metal projects.
Built from the same HSS material as the larger 5-piece set, with Rockwell 62–65 hardness and a four-flute geometry that keeps cuts manageable. You trade upper-range coverage for a smaller, easier-to-learn package, which is often the right call for someone still building confidence with step bits.
Notable Gains
- Three bits cover the small and mid-range diameters most beginners need first.
- Same HSS build and four-flute geometry as the larger 5-piece set, just at smaller sizes.
- Lower upfront cost for someone testing step bits before committing to a full set.
Where It May Fall Short
- Top diameter stops at 7/8″, so any larger knockouts need an additional bit like the Unibit M35 Cobalt 7/8″-1-3/8″.
- Standard HSS runs hotter in stainless and thick steel, which shortens usable life.
Built With In Mind
First-time step bit owners and DIYers focused on small pilot holes and light-gauge metalwork around the house.
Swap It Out When
Move up to the 5-Piece Unibit HSS Step Bit Set, 1/8″-1-3/8″ once you find yourself needing larger holes regularly.
Spec Overview
The Unibit HSS Step Bit Set, 1/8″-1-3/8″ (5-Piece) sits in the middle of the Bestwork range, offering the same full diameter coverage as the other 5-piece set in a slightly different configuration. Five bits walk from a 1/8″ pilot up to 1-3/8″, so most fabrication and garage jobs stay covered without buying extras.
The bits use the brand’s signature four-flute geometry for controlled chip evacuation, and the HSS body holds up to repeated cycles in mild steel, aluminum, and copper. It’s the dependable middle option between the budget 3-piece set and the higher-end cobalt picks earlier in this list.
The Upside
- Five bits deliver full 1/8″ to 1-3/8″ coverage for general fabrication work.
- Four-flute cutting geometry keeps cuts smooth and chips moving in standard HSS applications.
- Priced below cobalt alternatives, which helps when stocking a small shop.
Some Limits To Know
- Standard HSS construction loses hardness faster than the cobalt options in stainless and high-heat cuts.
- Bit variety may overlap with the 5-Piece Unibit HSS Step Bit Set, 1/8″-1-3/8″, so check sizing before doubling up.
Made For
General fabrication shops and home garages running a balanced mix of metalwork without specialty hard-alloy projects.
Where A Sibling Pick Shines
Reach for the Greenlee 34403 Multi-Hole Step Bit, 7/8″ instead, since you prefer a single-bit solution over managing a five-piece set.
At A Glance
What Matters Most Before Choosing Step Drill Bits For Metal
A step bit’s value shows up in the cut, not the catalog description, so focus on a few attributes that change how the tool feels in your hand. Material composition sits at the top: standard HSS handles mild steel and common non-ferrous metals, while M35 cobalt resists heat in stainless and thicker stock. Coating also matters, and TiAlN (titanium aluminum nitride) is the harder ceramic surface that lets the bit run cooler during long production runs.
Range and step count decide how flexible the bit is on real jobs. A bit that steps from 1/8″ to 1-3/8″ covers most residential electrical and plumbing holes, while smaller step counts (like Greenlee’s #1, #4, #9 trio) focus on trade-common diameters for faster tool changes. For fine increments, the Unibit M35 Cobalt 19-step bit walks through unusual conduit and knockout sizes in 1/32″ jumps.
Shank style and chuck fit round out the practical side. Standard round shanks fit any drill, while 3/8″ hex shanks lock into impact drivers and reduce slippage. A 1/2″ chuck (needed for the Greenlee GSB12 and similar large bits) becomes important once you step up to 1-3/8″ diameters, since smaller chucks won’t hold the larger bits securely.
Key Considerations Across These Picks
Common Shopping Slip Ups
A frequent misstep is buying a single multi-range step bit and expecting it to handle every material. Standard HSS bits cut mild steel and aluminum cleanly but run hot in stainless, so the bit dulls fast and the hole quality drops. Matching the bit material to the workpiece extends tool life noticeably.
Another trap is overlooking shank and chuck compatibility. Larger bits like the Greenlee GSB12 1-3/8″ Step Bit (#12) need a 1/2″ chuck, and forcing them into a 3/8″ chuck risks slippage and broken bits. Confirm your drill’s chuck size before committing to a single large bit.
What The Higher Tier Buys
Premium cobalt step bits like the toolant M35 and Unibit M35 command a higher price because they keep hardness at elevated temperatures, where standard HSS softens. For production work in stainless, hard aluminum, or thick steel plate, that heat resistance translates into more holes per bit and cleaner cuts.
Coating adds another layer of value. TiAlN-coated bits shed heat and reduce wear on the cutting edges, so the bit stays sharp across more duty cycles. The trade-off is a higher upfront cost, which makes more sense for shops that run step bits daily rather than occasional weekend projects.
Frequently Asked Questions
What is a step drill bit used for on metal?
A step drill bit lets you drill multiple hole sizes with a single tool by using a stepped, cone-shaped profile. Each “step” adds diameter, so you start with a small pilot and walk up to the final size in one continuous motion. That makes it useful for electrical boxes, conduit knockouts, plumbing holes, and any task where you’d otherwise swap several individual bits.
How is a step bit different from a regular twist drill?
A twist drill cuts one fixed diameter and needs pilot holes for larger sizes, while a step bit cuts several diameters in sequence. The stepped profile also deburrs the hole as it exits, leaving a cleaner edge than a standard twist drill in thin sheet metal.
Can step drill bits cut stainless steel?
Cobalt step bits like the toolant M35 and Unibit M35 cut stainless steel more reliably than standard HSS, thanks to heat resistance. Standard HSS step bits work on mild steel and aluminum but tend to overheat in stainless, which shortens life. Using cutting fluid and slower RPM helps both types last longer.
What does a split-point tip do on a step bit?
A split-point tip starts cutting on contact, so the bit doesn’t wander or skid across the workpiece. That matters when you’re working on smooth or curved surfaces where a regular tip would skate before biting. Greenlee’s split-step design and the Greenlee 34403’s split tip both rely on this geometry for accurate hole placement.
How long does a step drill bit typically last?
Lifespan depends on material, RPM, feed pressure, and the metal being cut. Cobalt bits in mild steel can last through hundreds of holes, while standard HSS bits in stainless may dull after a much shorter run. Letting the bit cool between holes, using lubricant, and avoiding excessive pressure all extend usable life.
